Photochromic compositions containing bleaching rate accelerators



United States Patent 3,355,294 PHOTOCHROMEC COMPOSITIONS CONTAININGBLEACHHNG RATE ACCELERATORS Sydney Arthur Giddings, New Canaan, Conn.,assignor to American Cyanamid Company, Stamford, Conn., a corporation ofMaine No Drawing. Filed Dec. 9, 1964, Ser.

No. 417,234 14 Claims. (CI. 96-90) ABSTRACT OF THE DECLOSUREPhotochromic compositions comprising an oxygen-containing polymer,certain metal compounds and various metal salts which, in solution, havean oxidation potential of from about -.30 to about 1.65 are disclosed.

(I) m n( )p wherein M is a transition metal, X is a halide, R'is analkyl radical having from -1 to 12 carbon atoms, inclusive, an arylradical having from 6-10 carbon atoms, inclusive, or a radical, R is analkyl radical having from 112 carbon atoms, inclusive, or an arylradical having from 6-10 carbon atoms, inclusive, m and p are whole,positive integers of from 06, inclusive, and n is a whole, positiveinteger of from 0-2, inclusive, the total of 2n-l-m-I-p being equal tothe valence of the metal M, at least one of m and p being an integer ofat least 1, and at least one of said polymeric material and said solventcontaining oxygen and (4) a bleaching rate increasing additive.

I have discovered that the bleaching rate of certain photochromiccompositions composed of plastic materials and certain transition metalcompounds can be materially increased by the addition of a specificgroup of additives thereto. The additives have been found to increasethe bleaching rate, i.e., the rate of color change of the compositionwhich has been irradiated, from its color caused by the irradiation backto its original color, as much as -50% over the bleaching rate of theuntreated composition. The compositions of the instant invention stillfunction photochromically in the form of various articles, such assheets, films and the like when subjected to ultraviolet light.

The use of photochromic materials as active ingredients in suchapplications as data storage devices, absorbers for incident,high-intensity radiation, photochemical printing, variable transmissiondevices and the like is well-known in the art. Compositions of matterwhich function photochromically and which may be utilized for thesepurposes are the subject matter of various patents. I have now foundthat compositions of matter composed of a polymeric material, a solventand a transition metal compound can be further enhanced so that they maybe utilized for additional applications wherein rapid bleaching ratesare essential, by the addition of a group of various bleaching rateincreasing additives thereto.

7 reading the more detailed 3,355,294 Patented Nov. 28, 1967 It istherefore an object of the present invention to provide novelcompositions of matter.

It is a further object of the present invention to provide novelcompositions of matter comprising a polymeric material, a transitionmetal compound and a bleaching rate increasing additive.

It is a further object of the present invention to provide compositionsof matter which are composed of a polymeric, resinous material, asolvent therefor, at least one of which contains oxygen, a transitionmetal compound represented by Formula I, above, and a bleaching rateincreasing additive, which compositions of matter are photochromic.

These and other objects of the present invention will become moreapparent to those skilled in the art upon description set forthhereinbelow.

Photochromism Molecules or complexes which undergo reversiblephoto-induced color changes are termed photochromic systems. That is tosay, in the absence of activating radiation, the system has a singlestable electronic configuration with a characteristic absorptionspectrum. When the system is contacted with ultraviolet irradiation, theabsorption spectrum for the system changes drastically, but when theirradiation source is removed, the system reverts to its original state.

Photochromism has been observed in inorganic and organic compounds bothin solution and solid state. Although the exart mechanism of colorchange varies markedly in each individual system, there are twoprocesses which account for most types of photochromic phenomena. Thefirst process is the transformation of excited state electronic energyinto vibrational and torsional twisting modes of the molecule. Usually,systems observed to be photochromic have very etficient routes forinternal transformation of absorbed energy and are generally neverfluorescent or phosphorescent. Internal transformation often takes placevery rapidly. That is to say, the primary process in thephoto-production of a colored species often occurs in about amillimicrosecond. However, optical observation of the colored speciesnormally takes considerably longer than this because of the very smallamounts of colored material produced per unit time and the depletion ofthe color by the competing reverse reaction.

The second fundamental photo-electronic mechanism generally consideredas producing photochromism is charge transfer. Most charge transferphenomena in organic molecules are rapidly reversible and thereforeproduce no colored intermediate. However, in inorganic crystals, chargetransfer absorption usually leads to a colored state in which thedonor-acceptor crystals have been oxidized and reduced.

There are three major factors which govern the behavior of aphotochromic system.

A. Absorption of incident radiation.According to the quantum theory,each absorbed quantum creates one activated molecule and only absorbedradiation can produce a chemical change. Variables which control thenumber of photons absorbed include the concentration and extinctioncoeflicient of the photochrome, the cell length, the screeningcoefficients of other components of the system, and the wavelengths ofthe incident radiation.

B. Quantum yieId.-All excited molecules will not undergo transformationto the colored form, so that the quantum yields will generally be lessthan unity. Various deactivating processes which compete for the excitedmolecules include fluorescence, phosphorescence, permanent chemicalchange and the thermal release.

C. The reverse 1eacti01z.In both the forward and reverse reactions, theconcentration of the colored form is dependent on the intensity of theradiation, the kinetics of the reverse reactions, and temperature andsolvent sensitivity of the reactions. The kinetics for the reversereaction will normally be controlling, however, some reverse reactionsare thermally sensitive and are accelerated by irradiation.

The terms photochromic composition or photochromic material, and thelike, as used in the instant disclosure, mean compositions or materials,etc., which change their transmission or reflectance upon beingsubjected to ultraviolet or visible irradiation and subsequently revertto their original state upon subjection thereof to a differentwavelength of radiation or removal of the initial ultraviolet source.

The ability of various materials to change color and to then revert backto their original color is not a new phenomena. In fact, such compoundshave been widely used in various ways, as described above. Generallythese compounds change their color when exposed to ordinary sunlight andrevert back to their original color upon removal thereof from the raysof the sun. Various other materials, however, change color only whensubjected to a certain degrce of irradiation, and as such, sunlight willnot eifect them. High intensity radiation, such as 25 cal./ cm. sec. ormore is necessary in regard to these compounds, while sunlight (O.2cal./cm. /sec.) will aifect the former.

The compositions of matter As mentioned above, I have found that thebleaching rate of various compositions of matter composed of a polymericmaterial and a transition metal compound represented by Formula I,above, can be increased by blending a group of specific bleaching rateincreasing additives therewith. I have further found that the presenceof a solvent for the polymer in these compositions is a materialadvantage. The only critical requirement in regard to the components inthe compositions of matter is that at least one of the polymer or thesolvent, if present, must contain oxygen, either in combined or freeform. That is to say, the compositions of the present invention arephotochromic when formed into shaped articles only when the plasticcomponent, the solvent component, or both, contain oxygen in some form,such as combined with the other elements of the component in question orin free form, i.e., as an added entity, e.g., an impurity or the like.Of course, when no solvent is employed in the compositions of matter,the polymeric component thereof must be the oxygen-containing portionbefore any photochromic phenomena can be observed.

Any thermoplastic resin can be used in the formation of our novelcompositions of matter. That is to say, any polymeric material,synthetic of naturally occurring, which is thermoplastic in nature andwhich may be dissolved in a solvent or made molten, may be used herein.Evidence of the types of polymers useful in our invention can beobtained from the more detailed description thereof set forthimmediately hereinbelow.

Examples of thermoplastic resinous or plastic materials which may beutilized in the preparation of the compositions of the present inventionare the various esters of acrylic acid and methacrylic acid, e.g., thosehaving the formula wherein R is hydrogen or a methyl radical and R is analkyl radical having from 1 to 6 carbon atoms, inclusive. Compoundswhich are represented by Formula II and consequently may be usedsingularly or in admixtures with one another, as monomers from which thepolymers used in the present invention may be produced include methylacrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butylacrylate, isobutyl acrylate, t-butyl acrylate, n-amyl acrylate, isoarnylacrylate, t-amyl acrylate, hexyl acrylate, methyl methacrylate, ethylmethacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butylmethacrylate, isobutyl methacrylate, t-butyl methacrylate, namylmethacrylate, isoamyl methacrylate, t-arnyl methacrylate, hexylmethacrylate and the like.

Other polymers which may be employed are those produced from styrenemonomers, e.g., those having the formula (III) R wherein R is hydrogenor a lower alkyl radical having 1 to 4 carbon atoms, inclusive, and R ishydrogen, a lower alkyl radical having 1 to 4 carbon atoms, inclusive ora halogen radical. Suitable monomers represented by Formula 111 includestyrene, methyl styrene, ethyl styrene, propyl styrene, o-, m-, orp-butyl styrene, o-, m-, or pchloro styrene, 0-, m-, or p-bromo styrene,o-, m-, or piluoro styrene o-, m-, or p-iodo styrene, a-methyl styrene,a-ethyl styrene, ot-butyl styrene, a-methyl-o-, mor pmethylstyrene,a-methyl-o-, mor p-ethyl styrene, a-butyl-o-, mor p-ethylstyrene,a-ethyl-o-, mor p-chlorostyrene, a-propyl-o-, mor p-iodostyrene and thelike.

Further examples of polymers which may be utilized to produce the novelcompositions of the present invention include polymers of acrylonitrile,polymers of acrylamide, polymers of vinyl halides such as poly(vinylchloride); polymers of vinylidene halides such as poly(vinylidenechloride); polymers of vinyl carbonate, vinyl alcohol, vinyl acetate,vinyl hutyral; polymers of various aldehydes, such as oxymethylene,acetaldehyde, crotonaldehyde; polymers of ethyleneoxide; cellulosepolymers such as cellulose acetate butyrate, cellulose triacetate, andany other polymeric material with which the transition metal compound iscompatible in the molten state and preferably which may be dissolved inan appropriate solvent.

Additionally, the monomers represented by Formulae II and III above, andwhich are disclosed hereinabove as useful for producing homopolymers canbe copolymerized either singly or in a plurality (two, three, four orany desired number), the latter often being desirable in order toimprove the compatability and copolymerization characteristics of themixture of monomers with themselves or various other copolymerizablemonomers to obtain copolymers having the particular properties desiredfor the particular service application. Examples of such comonorners arethe unsaturated alcohol esters, more particularly the allyl, methallyl,l-chloroallyl, 2-chlorallyl, cinnamyl, vinyl, methvinyl, l-phenylallyl,etc., esters of saturates aliphatic and aromatic monobasic and polybasicacids such, for instance, as acetic, propionic, butyric, valeric,caproic, oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic,azelaic, sebacic benzoic phenylacetic, phthalic, terephthalic,benzoylphthalic, etc., acids; vinyl naphthalene, vinylcyclohexane, vinylfurane, vinyl pyridine, vinyl dibenzofuran, divinyl benzene, trivinylbenzene, allyl benzene, diallyl benzene, N-vinyl carbazole, un saturatedethers, e.g., ethyl vinyl ether, diallyl ether, ethyl methallyl ether,etc.; unsaturated amides, for instance, N- allyl caprolactam,N-substituted acrylamides, e.g. N- methylol acrylamide, N-allylacrylamide, N-methyl acrylamide, N-phenyl acrylamide, etc; unsaturatedketones, e.g.,methyl vinyl ketone, methyl allyl ketone, etc.; methylenemalonic esters, e.g., methylene methyl malonate, etc.

Further examples of thermoplastic polymers useful in producing my novelcompositions are thermoplastic polyesters such as those produced byreacting a saturated aliphatic diol with a non-polymerizablepolycarboxylic acid to produce a polyester having an acid number notappreciably more than 75. Among the dihydric alcohols which may beemployed are saturated aliphatic diols such as ethylene glycol,propylene glycol, butylene glycol, diethylene glycol, dipropyleneglycol, triethylene glycol, tetraethylene glycol, butanediol-1,2,butanediol-1,3, butanediol-1,4, pentanedio1-l,2, pentanediol-1,3,pentanediol-1,4, pentanediol-1,5, hexanediol-1,2, hexanediol-1,3,hexanediol-1,4, hexanediol-1,5, hexanediol-1,6, neopentyl glycol, andthe like, as well as mixtures thereof. Among the polyols having morethan two hydroxyl groups which may be employed in minor amounts,together with the above-mentioned diols, are saturated aliphatic polyolssuch as glycerol, trimethylol ethane, trimethylol propane,pentaerythritol,dipentaerythritol, arabitol, xylitol, dulcitol,adonitol, sorbitol, mannitol, and the like, as well as mixtures thereof.

Non-polymerizable polycarboxylic acids, i.e., acids which are saturatedor which contain only benzenoid unsaturation, which may be used includeoxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic,sebacic, malic, tartaric, tricarballylic, citric, phthalic, isophthalic,terephthalic, cyclohexanedicarboxylic, endomethylenetetrahydrophthalic,and the like, as well as mixtures thereof.

The esterification mixtures, from which the thermoplastic polyesterresins employed in the practice of the present invention are prepared,are generally formulated so as to contain at least a stoichiometricbalance between carbonyl and hydroxyl groups. Thus, where a diol and adicarboxylic acid are employed, they are usually reacted at elevatedtemperatures and in an inert atmosphere, on at least a mole to molebasis. In common commercial practice, a small excess of polyol, usuallyin the range of from about 5 %to about 15% excess, is employed. This isdone primarily for economic reasons, i.e., to insure a rapid rate ofesterification.

Further details pertaining to the preparation of polyester resins of thetypes employed in the practice of the present invention are disclosed inU.S. Patent No. 2,255,- 313 to Ellis, and in U.S. Patent Nos. 2,443,735to 2,443,- 741, inclusive, to Kropa, and these patents are herebyincorporated into the present application by reference.

As further examples of polymeric materials which may be used to producemy novel compositions of matter are the polyamide resins, i.e., thoseproduced from a dibasic acid and a polyamine. Polyamide resins of thistype are well known in the art and are generally termed nylon resins.These nylon resins, as used in the instant specification, are long chainsynthetic polymeric amides which have recurring amide groups as anintegral part of the main polymer chain and which are capable of beingformed into a filament in which the structural elements are oriented inthe direction of the axes. Most common of these nylons or polyamides areobtained by condensation of a diamine with a dicarboxylic acid or byauto condensation of an amino acid. These polyamides have the structuralformula NH(CHz) NHCO(CH ),,CONH(CH x and y being greater than one.Methods for the production of polyamides of this type are shown, forexample, in the following patents: U.S. Patent Nos. 2,191,556;2,293,760; 2,293,761; 2,327,116; 2,359,877; 2,377,985; 2,572,843, saidpatents hereby being incorporated herein by reference.

Additionally, I may utilize such polymeric materials as thepolyurethanes. Any polyester based or polyether based polyurethane resinmay be used in the present invention. Among the reactive organicpolyfunctional polyols employed in preparing one class of polyurethaneresins used in the practice of our invention by reaction with a suitableisocyanate compound are the polyalkylene g, ether, thioether, andether-thioether glycols represented by the general formula wherein Rrepresents the same or difierent alkylene radicals containing up toabout 10 carbon atoms, X represents oxygen or sulfur, and z is aninteger large enough so that the molecular weight of the polyalkyleneether, thioether, or ether-thioether glycol is at least about 500, e.g.,from about 500 to about 10,000. The polyalkylene ether glycols includedwithin this general formula, such as polyethylene glycols, polypropyleneglycols, polybutylene glycols, polytetramethylene glycols,polyhexamethylene glycols, and the like, which are obtained, forexample, by aci-d-catalyzed condensation of the corresponding monomericglycols or by the condensation of lower alkylene oxides, such asethylene oxide, propylene oxide, and the like, either with themselves orwith glycols such as ethylene glycol, propylene glycol, and the like,are preferred.

Polyalkylenearylene ether, thioether and etherthioether glycols whichalso have molecular weights ranging from about 500 to about 10,000 butwhich differ from the above-described polyalkylene glycols in havingarylene radicals, such as phenylene, naphthylene and anthryleneradicals, either unsubstituted or substituted, e.g., with alkyl or arylgroups, and the like, in place of some of the alkylene radicals of saidpolyalkylene glycols may also be employed. Polyalkylene-arylene glycolsof the type ordinarily used for this purpose will usually contain atleast one alkylene ether radical having a molecular weight of about 500for each arylene radical present.

Essentially linear polyesters containing a plurality ofisocyanate-reactive hydroxyl groups constitute another class of reactiveorganic polyfunctional polyols which may be employed in preparingpolyurethane resins useful in the practice of the present invention.While the prepa ration of polyesters suitable for this purpose has beendescribed in great detail in the prior art and forms no part of thepresent invention per se, it may be mentioned here by way ofillustration that polyesters of this type may be prepared by thecondensation of a polyhydric alcohol, with a polycarboxylic acid oranhydride in the same manner as set forth hereinabove in regard to thedissertation on applicable polyester resins which may be used herein,with the same examples of reactants applying in both instances.

The essentially linear polyesters commonly used in preparingpolyurethane resins preferably have molecular weights ranging from about750 to about 3000. In addition they will generally have relatively lowacid numbers, e.g., acid numbers not appreciably in excess of about 60and preferably as low as can be practicably obtained, e.g., 2 or less.Correspondingly, they will generally have relatively high hydroxylnumbers, e.g., from about 30 to about 700. When preparing thesepolyesters, an excess of polyol over polycarboxylic acid is generallyused to insure that the resulting essentially linear polyester chainscontain a sufficient amount of reactive hydroxyl groups.

The polyurethane resins useful as a component of my novel compositionsmay be prepared using a wide variety of organic polyisocyanates, amongwhich there are included the aromatic diisocyanates, such asm-phenylenediisocyanate, p-phenylenediisocyanate,4-t-butyl-m-phenylenediisocyanate, 4 methoxy-m-phenylenediisocyanate,4-phenoxy-m-phenylenediisocyanate, 4 chloro-m-phenylenediisocyanate,toluenediisocyanates (either as a mixture of isomers, e.g., thecommercially available mixture of 2,4-toluenediisocyanate and 20%2,6-toluenediisocyanate, or as the individual isomers themselves),m-xy-' lylenediisocyanate, p xylylenediisocyanate, cumene-2,4-diisocyanate, durenediisocyanate, 1,4-naphthylenediisocyanate,1,S-naphthylenediisocyanate, 1,8-naphthylenediisocyanate, 2,6naphthylenediisocyanate, 1,5 tetrahydronaphthylenediisocyanate, p,p'diphenyldiisocyanate, di-

wherein 11 represents an integer between and about 5, and the like;aliphatic diisocyanates, such as methylenediisocyanate,ethylenediisocyanate, the tri-, tetra-, penta-, hexa-, hepta-, oct-,nonand decamethylene-md-diisocyanates, 2 chlorotrimethylenediisocyanate,2,3-dimethyltetramethylenediisocyanate, and the like, and triand higherisocyanates, such as benzene 1,3,5 triisocyanate, toluene2,4,6-triisocyanate, diphenyl-Z,4,4-triisocyanate,triphenylmethane-4,4',4-triisocyanate, and the like. Mixtures of two ormore of such organic polyisocyanates may also be employed to prepare thepolyurethane resins by reaction with the ethers and esters describedabove utilizing procedures well known to those skilled in the art, seefor example, US. Patents 2,729,618, 3,016,364 and the like.

As mentioned above, the polymer component of my novel compositions maybe used as a molten material or as a solution thereof in a solvent.While the use of a solvent is preferred, it is not critical. The actualsolvent employed in each instance is not critical except for the factthat it is preferred that the solvent contain an oxygen atom, asspecified above. Generally, any compound which is a solvent for thepolymer may be employed for this purpose in a sufficient amount so as todissolve the polymer employed, provided that at least the polymer or thesolvent contains oxygen, as mentioned above.

Examples of solvents which may be utilized include dimethyl formamide,acetonitrile, methylene chloride, glyme (CH OCH CH OCH diglyme (CH OCHCH OCH CH OCH chloroform, ethyl acetate, methylene chloride, trioxane,dioxane, ethyl formate, ethylene dichloride, isopropyl acetate, methylacetate, acetic acid, acetone, benzil, acetaldehyde, benzaldehyde, butylacetate, cellosolve, cyclohexanol acetate, cyclohexanone,methylethylketone, toluol, gamma-valerolactone, methanol, ethanol,hexanol, nitrobenzene, nitropropane, trichloroethylene, aniline,diacetone alcohol, ethyl lactate, carbon tetrachloride, pyridine,toluol, xylol, ethylene glycol, water and the like.

Additionally, any specific polymer may be dissolved in one of its ownconstituents so as to form a solution thereof. That is to say,poly(methyl methacrylate), for example, can be utilized as a solution ofthe polymer in methyl methacrylate. Likewise, the other polymersdisclosed hereinabove may also be used as solutions thereof in monomersfrom which they are produced.

Furthermore, mixtures of the above-mentioned solvents or other solventswhich conform to the requirements set forth herein, may be used tosolubilize the polymers. For example, methylene chloride and acetic acidin a 50/50 mixture may be used with poly (methyl methacrylate).

In many instances, the polymers, as a result of solvents used duringproduction thereof, or the solvents, as a result of affinity or weakbonding reactions, may contain a minor trace amount of an impurity suchas water and the like. In instances of this sort, no newly added solventneed be added to produce our novel compositions if the critical oxygenrequirement mentioned above has been fulfilled. By the term traceamounts or impurities is meant amounts as minimal as 0.1% are tolerableand 8 generally sutricient to enable the production of a photochromicarticle.

Examples of transition metal compounds which may be utililed inproducing the compositions of matter of the present invention and whichare represented by Formula I, include titanium tetrachloride, titaniumoxidedichloride, zirconium tetrachloride, zirconium oxidedichloride,tungsten hexachloride, tungsten oxidetetrachloride, tungstendioxidedichloride, hafnium tetrachloride, hafnum oxidedichloride,tantalum pentachloride, tantalum oxidetrichloride, tantalumdioxidechloride, titanium tetrabromide, titanium oxidedibromide,zirconium tetrabromide, zirconium oxidedimrobide, tungsten hexabromide,tungsten oxidetetrabromide, tungsten dioxidedibromide, hafniumtetrabromide, hafnium oxidedibromide, tantalum pentabromide, tantalumoxidetribromide, tantalum dioxidcbromide, titanium tetraiodide, titaniumoxidediiodide, zirconium tetraiodide, zirconium oxidediiodide, tungstenhexaiodide, tungsten oxidetetraiodide, tungsten dioxidediiodide, hafniumtetraiodide, hafnium oxidediiodide, tantalum pentaiodide, tantalumoxidetriiodide, tantalum dioxideiodide, titanium tetrafiuoride, titaniumoxidedifiuoride, zirconium tetrafiuoride, zirconium oxidedifluoride,tungsten hexafluoride, tungsten oxidetetrafiuoride, tungstendioxidedifluoride, hafnium tetrafluoride, hafnium oxidedifluoride,tantalum pentafluoride, tantalum oxidetrifluoride, tantalumdioxidefiuoride, chromium dioxide dichloride, chromium dioxidedimethoxide, vanadium oxide trichloride, vanadium oxide triiodide,vanadium dioxide bromide, vanadium dioxide methoxide, titaniumtetramethoxide, titanium tetraethoxide, titanium tetraheptoxide,titanium tetradodecoxide, titanium oxide dimethoxide, titaniumdichloride dimethoxide, titanium trichloride ethoxide, titanium chloridetrimethoxide, zirconium tetramethoxide, zirconium tetraphenoxide,zirconium tetra(ptolyloxide), zirconium tetra(naphtlioxide) ,l zirconiumoxide dimethoxide, zirconium oxide diphenoxide, zirconium dibromidediethoxide, zirconium trifiuoride butoxide, zirconium iodidetrimethoxide, hafnium tetraacetate, hafnium tetravalerate, hafniumtetralaurate, hafnium oxide diacetate, hafnium dibromide divalerate,hafnium trifiuoride laurate, hafnium chloride triphenoxide, tantalumpentamethoxide, tantalum pentabenzoate, tantalum penta(ptoluate),tantalum penta(2-naphthoate), tantalum oxide tribenzoate, tantalumdioxide methoxide, tantalum dichloride triethoxide, tantalumtetrabromide acetate, tantalum bromide tetraphenoxide, tantalumtrifluoride dimethoxide, tungsten hexamethoxide, tungsten oxidetetrabenzoate, tungsten dioxide diacetate, tungsten pentachloridemethoxide, tungsten tetrabromide bis(p-toluate), tungsten triiodide tris(p-tolyloxide), tungsten dichloride tetravalerate, tungsten bromidepenta(1-naphthoate) and the like. The amount of transition metalemployed may range from 0.01% to 50.0%, by weight, based on the weightof the polymer, preferably 0.1% to 25.0%, by weight, same basis.

The transition metal compounds listed above are all well known in theart and may be produced by any equally well known procedure. Examples ofapplicable methods for the production thereof appear in at least one ofthe following articles. Razivaer et al., Tetrahedron 6, 159 (1959);Sandho et al., Current Sci. (Ind.) 29, 222 (1960); Rosenheim, Ch.Nernst. Z. Anorg. Chem. 214, 220 (1933); Bradley et al., J. Chem. Soc.1634 (1953),

" and these references are hereby incorporated herein by reference.

The additives which increase the bleaching rate of the photochromiccompositions and form the crux of the present invention are defined asmetal salts which, in solution, have oxidation potentials of from about0.30 to about -1.65. The preferred metal salts are those which arecolorless since the use of such salts enables one to maintain the color,whether it be water-white or red, of the resin-solvent-transition metalcompound compositions to which they are added. The salts which possesscolor, however, may be utilized if the final color of the composition isnot critical and is not exactly the same as that to which thecompositions devoid of the additives will change when subjected toultra-violet light.

The amount of metal salts necessary toincrease the bleaching rate of thephotochromic compositions should. range from about 0.01 mol to about 5.0mols, preferably from about 0.1 mol to about 2.0 mols, of the metalsalts, per mol of the transition metal compound represented by FormulaI, above.

As mentioned above, the metal compounds which may be added to thephotochromic compositions to increase the bleaching rate thereof musthave an oxidation potential, in solution, of .30 to -1.6S, inclusive.Generally salts of iron, thallium, manganese, cerium, rhodium, iridiumand the like fall within these limits with such anions as the halides,i.e., chlorides, bromides, fluorides, iodides, the sulfates, thenitrates, oxylates, acetates, propionates, benzoates and the like beingexemplary. That is to say, any salt which is formed by any cation andany coanion and has an oxidation potential within the above mentionedrange may be used in my invention. Examples of salts which may be usedinclude ferric chloride; ferrous chloride; ferric bromide; ferrousbromide; ferrous fluoride; ferric fluoride; ferric iodide; ferrousiodide; ferric sulfate; ferrous sulfate; ferric nitrate; ferrousnitrate; ferric oxylate; ferrous oxylate; ferric acetate; ferrousacetate; ferric propionate; ferrous propionate; ferric benzoate; ferrousbenzoate; sodium arsenate; potassium arsenate; thallium chloride,iodide, fluoride, bromide, sulfate, nitrate, oxylate, benzoate, acetateand propionate; manganese bromide, chloride, iodide, fluoride, acetate,propionate, oxylate, benzoate, sulfate; and nitrate; ceric and cerouschloride;"-'bromide, iodide, fluoride, sulfate, nitrate, oxylate,acetat'efbenzoate, "and propionate; rhodium chloride, bromide, iodide,fluoride, sulfate, nitrate, oxylate, acetate, benzoate and propionate;potassium iridium chloride, bromide, iodide, fluoride, sulfate, nitrate,'oxylat'e, benzoate 'and propionate; cupric and cuprous chloride,bromide, iodide, fluoride, acetate, propionate, benzoate nitrate,sulfate and oxylate and the like. I

The order of the addition of the components to form my novelcompositions is not critical and, furthermore, any method of blendingmay be used. For example, the solvent may be added to the polymer andthen the transition metal compound and metal salt additive may be addedor, alternatively, the transition metal compound and solvent may beblended and'the resultant solution may then be blended with the resintoproduce a composition to which may then be added the metal salt additiveand so forth. If the polymer is used in a molten state in the absence ofa solvent, however, the transition metal compound may be added theretoas such or as a mixture with the metal salt additive. The components maythen be thoroughly admixed by utilizing such means as a Waring Blender,a ball mill, a rubber mill or the like, the specific device utilized forthe blending in each instance forming no part of the instant invention.

Additionally, it is within the scope of the instant invention to formthe compositions of matter claimed herein by first blending theoxygen-containing polymer (or other polymer if an oxygen-containingsolvent is used) and solvent with the transition metal compound andmetal salt to form a substantially uniform blend, precipitating theblend into a non-solvent for the polymer, transition metal compound andmetal salt and recovering the resultant precipitate-d photochromiccomposition. Such a procedure is disclosed and claimed in copendingapplication, Ser. No. 399,087, filed Sept. 24, 1964, which applicationand any other application or patent referred to herein is herebyincorporated herein by reference.

A further method for incorporating the metal salts ihto the compositionsof the present invention is to contact an oxygen-containing monomer (orother monomer if an oxygen-containing solvent is used), solvent,transition metal compound and metal salt with a polymerization catalystunder polymerizing conditions. By utilizing the method, which isdisclosed and claimed in copending application Ser. No. 399,101, filedSept. 24, 1964, a polymeric composition is recovered which isphotochromic and has an increased return rate.

The novel compositions of the instant invention may be cast into filmsfrom a solution of the solvent by drawing the composition down on aself-supporting substrate such as glass, metals, such as steel, tile andthe like, a resinous material such as polyethyleneglycol terephthalate,paper, cellophane, marble, wood, leather, cloth and the like, or merelycasting on any solid surface and removing the resultant film. The thinfilm which is deposited by casting in this method generally should rangein thickness from about 0.1 mil to about 1000 mils, preferably 0.5 milto about 125 mils, to produce an optimum photochromic effect.

The exact phenomena which occurs upon blending the components of thecompositions claimed herein is not completely understood. It is knownhowever, that the compositions are not photochromic unless at least thethermoplastic resin or the solvent, or both, contain oxygen, in free orcombined form, and until the compositions are formed into a definiteshaped article, such as by casting. While we do not wish to be bound byany explanation of the photochromic mechanism which results or theory inregard thereto, it is possible that the active material may be formed bythe formation of a metal adduct with the polymer. For example, utilizingpoly(methyl methacrylate) and tungsten hexachlon'de, thephotochromismcould possibly result by formation of a tungsten additionproduct wtih a reactive oxygen in the polymer. The same result couldalso occur when the solvent present, if any, has a reactive oxygentherein.

The scope of the present invention is also of such breadth so as toinclude the use of such modifying rnaterials as fillers, lubricants,plasticizers, stabilizers, antioxidants and the like as additives to thenovel compositions claimed herein in addition to ultraviolet lightabsorbers. The novel compositions of the present invention may be usedto produce such articles as plastic window panes, sky lights, automobileWindshields, sunglass lenses, memory devices such as optical analoguecomputers, temporary osscillographs, temporary photographic proofs,photographic marking devices, light switches, optical masks, wallpanels, jewelry, toys, advertising articles and the like.

The following examples are set forth for purposes of illustration onlyand are not to be construed as limitations on the instant inventionexcept as set forth in the appended claims. All parts and percentagesare by weight unless otherwise specified.

EXAMPLE I A composition of matter is produced by blending 20 parts ofpolymethylmethacrylate, dissolved in parts of dioxane, with 2.5 parts oftungsten hexachloride. To this composition of matter are then added 0.25mol of FeCl per mole of tungsten hexachloride. The resultant solution isstirred, filtered and then cast as a film, 20 mils in thickness, on asheet of commercially available polyethyleneglycol terephthalate. Thefilm is dried and, when irradiated with ultraviolet light, changes fromcolorless to blue. The bleaching (optical density) of the film from blueto'colorless is then measured in a spectrophotometer after 30 minutes inthedark and at room temperature. The results of Example 1 and ofadditional metal salt additives, solvents, polymers and transitionmetals are set forth in Table Ibelow.

TABLE I Ex. Metal Salt Oxidation Mols 1 Polymer Transition Metal SolventPercent 2 RC.

Additive Potential Additive Compound Bleached 1 FeCh PMMA W014i 0.60Yes. 2 PMMA. W 01 0.72 Yes. 3 NazHASO; PMMA. Vv'Clt 0. 51 Yes. 4 'IlClPNILIA. \VC-la 0.61 Yes. 5 M11011 PMMA. W01 0. 45 Yes. 6 M!1(O-CCH3)1Polystryene W001; 0. 47 Yes.

7 Ce(SO4)z 1.61 0.50 Thermoplastic polyester NhOlt Dimethyl sulloxide...0. 50 Yes.

resum 8 T101 -1. 25 0.20 Cellulose acetate Ti(OH3)4 Acetone 0.58 Yes. 9RhCla -1. 46 0.10 Polyurethane resin. ClOzClz Dimethyl formamide... 0.51 Yes. 10. KalrCl 1.02 0.20 Poly (acrylamide). NbOIa Ethylene glycol.0.45 Yes. 111 M1101 1. 51 0.15 Poly(vinylacetate) WO2(OIzHs): 0. 49 Yes.12. FeCla -0. 77 0.10 Poly(acrylic acid). ZrCh Methylethyl ketoue. 0.58Yes. 13 T101 -1. 25 0.15 Poly(oxymethylene) 'IaClt one 0.58 Yes. 1 LT101 1. 25 0. 50 Poly(methylacrylate) WBI'G Dioxane 0.55 Yes. 15.Mn(0fi301h)g 1. 51 0.10 Cellulose acetate butyrate. TlOFzGamma-valerolacetone. 0.52 Yes.

16- NayHASO, 0. 56 0. Polytvinylbutyral) HfI4 Acetic acid 0. 50 Yes.n0]: --1. 51 0. Poly(acetaldehyde) WFG 0. 46 Yes.

AgCls 1.98 0. 2O P1\1MA WCle 0. 73 Yes.

Fe 01 -O. 77 O. Polyacrylo V0 (0 01H); Dimctuyl formamide. 0. 61 Yes.

T101 1. 25 0.10 Polyalnide resin ZYBTQ(OCZH5)3 Benzyl alcohol- 0. 59Yes.

KQII'Ola 1.02 0.15 Polyvinylchloride TaOIa None 0.00 No.

II 23. MnCl: 1. 51 0.30 TeAr l plyrlr gr MMA/STI WI (OC-0 116),Methylethyl kctoue... 0. 48 Yes 60 20. 24 NaHASO; 0. 56 0.20Polycarbonate resin 0 T1014 Ethylene dichloride 0. 56 Yes 1 Per mol oftransition metal compound. 6 Commercially available carbonate resinproduced from reacting 2 Optical density of sample measured inspecrophotometer after minutes in the dark at room temperature. 1.00indicates no bleaching and 000 indicates complete bleaching.

3 Commercially available polyester resin produced from 50% phthalicacid, 25% diethylene glycol and 25% dipropylene glycol.

4 Commercially available polyurethane resin produced by reacting apolyester resin of diethylene glycol, hexanediol-1,3 and phthalic acidwith 2,4-toluenediisocyanate.

B Commercially available polyamide resin produced from hexamethylenediamine and adipic acid.

I claim:

1. A composition of matter comprising (1) a polymer, (2) a solventtherefor, (3) a metal compound having the formula MX O (OR) wherein M isa metal selected from the group consisting of titanium, zirconium,tungsten, hafnium, tantalum, zirconium, chromium, vanadium and niobium,X is a halide, R is selected from the group consisting of an alkylradical having from 1-12 atoms, inclusive, an aryl radical having from610 carbon atoms, inclusive, and

R is selected from the group consisting of an alkyl radical having from1-12 carbon atoms inclusive, and an aryl radical having from 6-10 carbonatoms, inclusive, m and p are whole positive integers of from 0-6inclusive, and n is a whole positive integer of from 0-2, inclusive, thetotal of Zn plus in plus p being equal to the valence of the metal M, atleast 1 of m and p being an integcrof at least 1, at least one of saidpolymer and said solvent containing oxygen, and (4) 0.01 mol to 5.0mols, per mol of (2), of a metal salt which, in solution, has anoxidation potential of from about .30 to about 1.65.

2. A composition according to claim 1 wherein said polymer ispoly(mcthylmcthacrylate 3. A composition according to claim metalcompound is tungsten hcxachloridc.

4. A composition according to claim solvent is dioxane.

5. A composition according to claim 1 wherein said polymer ispoly(mcthylmcthacry-late), said solvent is dioxane and said metalcompound is tungsten hcxachloride.

6. A composition of matter according to claim 1 wherein said polymer ispoly(methylmcthacrylatc said metal- 1 wherein said 1 wherein saidphosgenc with bisphenol A to give product having u structure wherein Mis a metal selected from the group consisting of titanium, zirconium,tungsten, hafnium, tantalum, zirconium, chromium, vanadium and niobium,X is a halide, R is selected from the group consisting of an alkylradical having from 112 atoms, inclusive, an aryl radical having from6-10 carbon atoms, inclusive, and

C Rl R is selected from the group consisting of an alkyl radical havingfrom l-l2 carbon atoms, inclusive, and an aryl radical having from 61()carbon atoms, inclusive, m and p are whole positive integers of from 0-6inclusive, and n is a whole positive integer of from 02, inclusive, thetotal of 211 plus m plus p being equal tothc valence of the metal M, atleast 1 of m and p being an integer of at least 1 and (3) 0.01 mol to5.0 mols per mol of (2), of a metal salt which, in solution, has anoxidation potential of from about .30 to about 1.65.

10. A composition according to claim polymer ispoly(methylmethacrylate).

11. A composition according to claim metal compound is tungstenhcxachloride.

12. A composition according to claim 9 wherein said polymer ispoly(mcthylmethacrylatc) and said metal compound is niobiumpcntachloride.

13. A composition according to claim 9 wherein the metal salt ismangancous chloride.

9 wherein said 9 wherein said 13 14 14. A composition according to claim9 wherein the Carbonyls, Jr. Phys. Chem., 68, 433-4 (1964), 9690 metalsalt is thallo'iis chloride. PC.

Singh, G.: Phototropy of Inorganic Salts, J. Chem.

References Cited Soc., 121, 782-5 (1822), 96-90 PC. Brown, G. H.:Phototropy, A Literature Review, De- 5 cember 1959, AD #234,009, pp.18-20, 96-90 P C, RMAN G. TORCHIN, Primary Examzner.

El-Sayed, Ne'vi Class of Photochromic Substances: C. E. DAVIS,AssistantExaminer.

1. A COMPOSITOR OF MATTER COMPRISING (U) A POLYMER, (2) A SOLVENTTHEREFOR, (3) A METAL COMPOUND HAVING THE FORMULA